[gcc r16-353] libstdc++: Add missing feature-test macro in <memory>

[Jonathan Wakely]

https://gcc.gnu.org/g:0e65fef8717f404cf9c85bff51bf87d534f87828

commit r16-353-g0e65fef8717f404cf9c85bff51bf87d534f87828
Author: Dhruv Chawla <dhruvc@nvidia.com>
Date:   Tue Apr 8 01:01:24 2025 -0700

    libstdc++: Add missing feature-test macro in <memory>
    
    Per version.syn#2, <memory> is required to define
    __cpp_lib_addressof_constexpr as 201603L.
    
    Bootstrapped and tested on aarch64-linux-gnu.
    
    Signed-off-by: Dhruv Chawla <dhruvc@nvidia.com>
    
    libstdc++-v3/ChangeLog:
            * include/std/memory: Define __glibcxx_want_addressof_constexpr.
            * testsuite/20_util/headers/memory/version.cc: Test for macro
            value.

Diff:
---
 libstdc++-v3/include/std/memory                          | 1 +
 libstdc++-v3/testsuite/20_util/headers/memory/version.cc | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/libstdc++-v3/include/std/memory b/libstdc++-v3/include/std/memory
index 99f542dcddc6..78a1250d29a1 100644
--- a/libstdc++-v3/include/std/memory
+++ b/libstdc++-v3/include/std/memory
@@ -97,6 +97,7 @@
 #  include <bits/out_ptr.h>
 #endif
 
+#define __glibcxx_want_addressof_constexpr
 #define __glibcxx_want_allocator_traits_is_always_equal
 #define __glibcxx_want_assume_aligned
 #define __glibcxx_want_atomic_shared_ptr
diff --git a/libstdc++-v3/testsuite/20_util/headers/memory/version.cc b/libstdc++-v3/testsuite/20_util/headers/memory/version.cc
index c82c9a018e0a..946955dd2123 100644
--- a/libstdc++-v3/testsuite/20_util/headers/memory/version.cc
+++ b/libstdc++-v3/testsuite/20_util/headers/memory/version.cc
@@ -6,3 +6,7 @@
 #if __cpp_lib_allocator_traits_is_always_equal != 201411L
 # error "Feature-test macro __cpp_lib_allocator_traits_is_always_equal has wrong value in <version>"
 #endif
+
+#if __cpp_lib_addressof_constexpr != 201603L
+# error "Feature-test macro __cpp_lib_addressof_constexpr has wrong value in <version>"
+#endif